This rather long entry is the delivery of a promise I made to slashbart when he asked me to read a paper by Nir Shaviv in this thread. I invite slashbart (Bart), his collegue Bas van Geel (Professor of Paleo-Ecology of the University of Amsterdam), or anyone else to comment but I ask that the conversation be kept civil as was the case in the linked thread.

To use Bart's words, Bart and Bas are "completely unconvinced about CO2 being such an important factor [in climate change]". There are quite a few good links in the thread but the main thrust of this post is centered around the Shaviv paper and the cosmic ray theory which Bart believes supports his stance, I will also take Bart to task over some other bits and pieces mentioned in the thread. But first of all let's state a few points I belive we have agreed on, the majority of which are based on Bart's words in the original thread.

1.The three of us are all genuine skeptics who belive the philosphy and practice of science trumps all other "ways of knowing" such as religion, intuition, etc. We believe that questioning our own assumptions and assertions is a crucial ingredient of any self respecting skeptic. Without this understanding there is no basis for reasoned debate and thus no point in debating.
2. Sugar in the petrol tank does not harm one's engine...
3.Climatologists have (correctly) discounted the change of TSI as the cause of the warm late 20th century.
4.Clouds and solar forcing have a "very low LOSU" as defined in the IPCC reports.
5.There are awfully complicated feedback mechanisms (plant growth, albedo changes, clouds, aerosols,...) ie: there is a low-very low LOSU of these feedbacks.
6.It's an excellent idea to start living more energy efficient lives, but we don't need to get all panicky, and we really shouldn't begin geo-engineering efforts when we really don't know what we're messing with. I further assume this includes our current uncontrolled geo-engineering in the form of GHG emmissions and other nastier chemicals which are relesed as a result of burning fossil fuels, in particular coal.
7.Science is not in the business of "proof" and is never "settled".
8.We all have scientific training and a keen interest in climate but none of us are climatologists. Bart is a Physicist, Bas is a Proffesor of paleo-ecology and I have a BSc with majors in computer science and operations research.
9.There exists what I call psuedo-skeptics, people who deliberatly misinform and mislead the public for political or financial gain in much the same way as tabacco companies did prior to the 1990's and for pretty much the same reason. None of us are psuedo-skeptics, none of us are totally immune from their carefully constructed bullshit. Andrew Bolt from Australia and George Will from the US are two fine examples of what a psuedo-skeptic is under my definition.
10.A large part of the IPCC work has to do with collecting climate change data, and not with the causes of that change. I agree in fact it is more than a large part your statement nicely sums up it's stated goals, of course that data is peer-revived to a very stringent criteria and the cases and likely effects from those papers goes into the SPM.

Bart, Bas, please activate your bullshit detectors if you have not already done so and I will breifly describe my understanding of (and problems with) the Shaviv paper, the cosmic ray theory and some related topics, please don't take anything I say as personal criticisim I am simply trying to appeal to your skepticisim and capacity for introspection. Why? - Because I think it is important to my grandchildren that scientifically minded people understand the issue of climate change to the best of their abilities and communicate their knowledge and understanding to the public as both Bart and I have done here on slashdot.

I read the paper quite dillegently but I admit I skimmed over the maths, it's no use going down to that level of detail because in all likelihood it is correct as most papers are if you accept their assumptions. So let's examine the assumptions. They make quite a few explicitly stated assumptions there is one thay make repeatedly that is at the heart of the matter ie: "that the CRF is indeed a climate driver".

They state this assumption even more strongly as: "We will not dwell here on the actual mechanism responsible for CRF link with cloud behavior. We will simply assume henceforth that this link exists, as supported by empirical and experimental data, even though it is still an issue of debate. This point has to be kept in mind since the conclusions we shall reach, will only be valid if this assumption is correct." (My emphasis).

Now as you have pointed out this effect has been observed in the laboratory and I am not disputing that. However in our intial debate you state: "I know about the laboratory scale effect of CO2. However, what is far from [certain] is how far this effect is actually influencing climate, because of the awfully complicated feedback mechanisms (plant growth, albedo changes, clouds, aerosols,...) ". Correct me if I'm wrong but this statement seems to indicate that a lab result is not enough because you think that in the real world other (agreed) problems make it impossible to apply the results from the lab. I think you need to look at that argument with some self-skeptical introspection, ie: why are you so willing to apply the (observed in the lab) cosmic ray effect to the 'real world' but dismiss the much more robust (observed in the lab) greenhouse effect in the 'real world'?

Papers that actually do some testing of Shaviv's assumption seem to be quite rare, (note I only have access to free pubs and abstracts on the net). However there is a plethora of papers that attempt to test and quantify the CO2 causal link in the real world such as the one I linked to above or this simplistic search

Let's move out a bit from examining the trees and look at the cosmic ray idea in more general terms. As I understand it basically goes something like this: The debateable link between cloud cover and cosmic rays says that an increase in CRF will create more (longer lasting?) clouds, clouds reflect the Sun's rays ( ie: higher albido ) and thus the Earth cools, I belive it has been refered to as the Iris effect. I checked out your claim of increased CRF over the last decade and it seems my assertion of no trend was (slightly) out of date although I was speaking of the pre-2000 ground based observations I did not state that clearly, here is the evidence at NASA

It basically says the Ulysees spacecraft has recorded a drop in solar wind, it is now 13% cooler and 20% less dense than a decade ago, this in turn means that it's ability to deflect the CRF been reduced and therefore a higher CRF should be observed on Earth (as you have claimed). It also goes on to say a 30% drop in the Sun's magnetic field strength has also been observed and that this further enhances the CRF reaching the Earth. This certainly is very interesting but I don't think it means what you think it does...

First of all the reduced solar wind should have some cooling effect, secondly according to the CR theory increased CRF should add to that cooling. However as I stated in the original debate the hottest 10yrs on record have all occurred within the last 12yrs, the evidence for this is found at the Hadley Center and is backed by the WMO and NASA amoung others. Ignoring the CRF for the moment the expected cooling from the reduced solar wind should by itself have been observed as a cooler Earth but since this is not the case it's lends some credence to my claim that the IPCC reports err on the side of caution (ie: they are conservative estimates).

Now in the original debate you dismissed M. Mann as being an activist. You also accused him of intolerance of opposing views with the line "You will not find information that disagrees with Michael Mann [at realclimate], unless he has managed to really stomp the counter arguments into the ground". This is simply false as I demontrated in the original debate and can be seen by actually reading any of his posts. Personally I would have thought stomping on counter arguments as I am doing here would be a good trait for a scientist and skeptic provided the boots you use avoid ad-homs and are intellectually honest.

ALL the IPCC reports are written soley by scientists and are generally accepted to represent the "best science available" on the issue, ie: they analogous to a text book written by 2500 scienists representing the vast majority of the world's scientific bodies who review all the litrature over a four year cycle. Your stated reason for dimmising the IPCC out of hand was "Also the politicised nature of the IPCC where its chairman calls Svensmark 'irresponsible' because his ideas don't fit in the consensus is insane, and thoroughly discredits its summary for policymakers."

I tend to agree with the chairman but not with the words you put in his mouth, I cannot see calling Svensmark 'irresponsible' discredits the entire IPCC or anyone else, a thorough stomping of Svensmark's CR ideas can be found at physicsworld. It's interesting to note that Svensmark decided to use a ghost authour to write his book "The Chilling Stars" in which he praises himself heavily in the third person.

I do not know why you choose to believe Svensmark and Shaviv or why you choose to dismiss the mountain of evidence collected by the IPCC and the large body of work that preceded them that streaches all the way back to Fourier in the early 1800's. There is certainly no scientific reason for that attitude and again I think you need to look at that with a healthy dose self-skeptical introspection.

The last major beef I have with our debate was your off-hand dissmisal of models with this comment: "As far as the modelling goes. I have built too many models to trust them when the basic science is not understood in detail. It's dead easy to model something that models the past, just put in enough parameters." First of all it's is not "dead easy" to reconstruct climate since you first have to get yourself tens of millions of dollars to buy the hardware as a number of institutions around the world have done, not the least of these is Japan's Earth Simulator.

Your comment seem to indicate you believe that this is all about twiddling statistcal parameters until it looks good, this is not the case and if that is how you build your numerical models I can tell you with a great deal certainty you are doing it wrong. I pointed to what I consider an exceptional demonstration of the power of these models in the original debate, if you did look at the site the fact of the matter is the computer you used to do so would have been impossible to build without the use of computer models. Again I think you need to look at your reasons for dismissing models that have proved their worth time and again in a vast array of endevours with a healthy dose self-skeptical introspection.
One last tip: "G'day mate" means hello not goodbye.